The invention relates to a control device for the drive motor of a windshield-wiper device of a vehicle, particularly a motor vehicle, having a control circuit, which can be activated by a manually-operated wiper switch, and automatically controls the drive motor, in a switching stage of the wiper switch, according to a characteristic curve and as a function of a signal of a rain sensor.
JP Abstracts 5-221290 (A) discloses a moisture-controlled windshield-wiper device of the above mentioned type, in which the switching threshold can be altered by means of manually-operated control elements, namely the windshield-wiper selector switch. Two different counters detect how frequently the windshield-wiper selector switch is operated. The one counter detects the switching processes into a higher operating mode, while the other counter detects the switching processes into a lower operating mode. An evaluation circuit reads out the contents of the counters, and raises or lowers the switching threshold for operating the wiper in interval operation. Here, a switch into a higher operating mode effects a lowering of the switching threshold, and thus a shortening of the pause between two wiping actions, whereas a switch into a lower operating mode effects a raising of the switching threshold, and thus a lengthening of the pause between two wiping actions. In interval operation, the windshield-wiper control permits an adaptation of the wiper intervals to the individual wishes of the user.
U.S. Pat. No. 5,568,027 discloses a control device for the drive motor of a windshield-wiper device of a vehicle, particularly a motor vehicle, having a control circuit that can be activated by means of a manually-operated wiper switch, and automatically controls the drive motor in a switching stage of the wiper switch, corresponding to a characteristic curve and as a function of a signal of a rain sensor. The windshield-wiper control avoids abrupt transitions in the wiper movement by using a smoothing algorithm to compare short-time rain-sensor signals, which experience statistical scattering, to the long-time signal behavior of the rain sensor, and by achieving smoothing through the formation of an average value of the long-time behavior of the rain sensor with the short-time behavior of the rain sensor. Furthermore, in interval operation, the wiper control is adapted to the logarithmic perceptive behavior of a person. For this purpose, the logarithm is formed from the counting value of the rain sensor in a microcomputer. This rain intensity, whose logarithm has been taken, is required as a counting value in the smoothing algorithm for further calculations. In interval operation, the driver has the opportunity to influence the value of the rain intensity, whose algorithm has been taken, by selecting a sensitivity pre-selection, and thereby adapt the interval control, to a limited extent, to his personal sensibilities. A characteristic-curve operation is not known from U.S. Pat. No. 5,568,027, however, because the value for the rain intensity is re-calculated every 0.3 seconds. Depending on the quantity of rain that impacts the windshield to be wiped, and is detected by the rain sensor, the pause length between each wiping cycle is reduced as the quantity of rain increases. If the pause length falls below a predetermined value, the drive motor is switched into continuous operation, in which its rpm is initially at a minimum value, and is increased to a maximum rpm with a correspondingly increased wiping-cycle number per time unit as the quantity of rain continues to increase.
In a control device of the type originally described, it is the object of the invention to implement measures that permit the adaptation of the wiping characteristic to the individual wishes of the user in all operating modes, specifically in interval operation as well as continuous operation of the windshield-wiper device.
In accordance with the invention, the above object generally is achieved by a control device for the drive motor of a windshield-wiper device of a vehicle, particularly a motor vehicle, having a control circuit, which is activated by a manually-operated wiper switch, and automatically controls the drive motor in a switching stage of the wiper switch according to a characteristic curve and as a function of a signal of a rain sensor, and wherein the control circuit pivots in the characteristics curve about an upper end point in response to switching operation of the manually-operated control element of the wiper switch. Further embodiments of the invention are disclosed and described.
In one embodiment of the control device according to the invention, an adaptive wiping characteristic curve is generated, and altered by manually-operated control elements if it does not correspond to the individual needs of the vehicle user. Here, the pause between two wiping actions in interval operation can be altered, and/or the rpm of the drive motor, or the wiping frequency, can be increased or decreased in subsequent, continuous wiping operation. For this purpose, the wiper switch is preferably equipped with the customary three switching stages; the automatic characteristic-curve operation is associated with the first switching stage, while one rpm or a plurality of fixed rpms is specified for the additional switching stage(s). The operating data for the control of the drive motor of the windshield-wiper device, which are established on the load side in the characteristic curve, are programmed to correspond to average requirements. After the automatic characteristic-curve operation has been initiated, an interval operation with long pauses is automatically controlled as a function of the quantity of rain detected per time unit by a rain sensor when the quantity is small; as the quantity of rain increases, the pause length decreases, and as the quantity of rain increases further, the drive motor is switched to continuous operation, in which the rpm is increased to a maximum value as the quantity of rain increases correspondingly.
If the predetermined characteristic curve is not controlling a wiper characteristic that corresponds to the personal wishes of the driver, the characteristic curve can be altered through the initiation of the additional switching stages of the wiper switch. If, for example, the pauses are too long in interval operation, or the wiping frequency is too low in continuous operation, the wiper switch need merely be switched to one of the further switching stages with preset rpms. This switching measure is detected in the control device, and an adaptation-algorithm control that is thereby activated reduces the inclination of the characteristic curve. The end point of the characteristic curve remains at least predominantly fixed in the maximum operating point of the drive motor. This upward pivoting of the characteristic curve about the maximum operating point changes the drive-motor operating data, which are associated with the characteristic curve, such that the pauses in interval operation are respectively shortened, and the rpm of the drive motor, or the wiping frequency of the windshield wiper, is increased in the characteristic-curve segment for continuous operation. In this case, the delay-switching of the wiper switch from the switching stage 1 into the switching stage 2 can effect a preset change, while a more dramatic elevation of the characteristic curve, in contrast, can be controlled in a through-switching from the switching stage 1 to the switching stage 3. Repeated back-switching to new delay-switching of the wiper switch can effect a stage-wise elevation of the characteristic curve or a decrease in the inclination of the characteristic curve by means of the algorithm control. Thus, back-switching of the wiper switch into the first switching stage for automatic operation creates a characteristic curve for rain-dependent control of the windshield-wiper device that approximately matches the driver""s needs.
If, in contrast, the operating point on the rain-quantity-dependent characteristic curve provides the drive motor with operating data that result in a too-frequent wiping sequence for the driver""s individual needs, it is possible to retract the characteristic-curve data in such a way that the curve inclination again increases steeply, the pause lengths in interval operation become larger and the wiping frequency in the characteristic-curve region above this is slowed. Here, it is assumed that the current characteristic curve for automatic operation that is dependent on the quantity of rain is actuated in a region located above the number of wiping cycles, or the rpm of the drive motor, that the switching position 2 of the wiper switch presets. Accordingly, if the user switches the wiper switch from the switching position 1 specified for automatic operation to the switching position 2, the operating data predetermined by the switching position 2 lie below the operating data predetermined by the current characteristic curves.
In the algorithm control, the obtained control signal effects a reduction in the operating data, not merely for this operating point, but over the entire characteristic-curve quantity. In the process, the highest operating point of the characteristic curve, which is associated with the largest detected quantity of rain, again remains unchanged. A new characteristic curve can be determined, or a shift can be made to one of a plurality of predetermined characteristic curves. In addition, if the wiper switch is switched into its zero position, and the rain sensor continues to signal a significant quantity of rain as the vehicle engine runs, a control command that is thereby obtained can be used to increase the inclination of the characteristic curve, or change its course such that the pauses in interval operation are lengthened, and the continuous wiping cycles in the upper region of the characteristic curve are reduced.
The invention is described below by way of schematic representations.